Marine organisms have been the source of many steroids and a number of groups which have chemical and pharmacological activity.
An article in Journal Organic Chemistry, 1992, 57, 2996-2997, entitled "Two Unique Pentacyclic Steroids with Cis C/D Ring Junction from Xestospongia bergquistia Fromont, Powerful Inhibitors of Histamine Release", N. Shoji et al., discloses xestobergsterol A (1) (23S-16.beta., 23-cyclo-3.alpha.,6.alpha.,7.beta.,23-tetrahydroxy-5.alpha.,14.beta.-chole stan-15-one) and B (2) (23S-16.beta.,23-cyclo-1.beta.,2.beta.,3.alpha.,6.alpha.,7.beta.,23-hexahy droxy-5.alpha.,14.beta.-cholestan-15-one), potent inhibitors of histamine release from rat mast cells induced by anti-IgE, are the first report of steroids with both the C.sup.16 /C.sup.23 bond and cis C/D ring junction.